The present invention relates to a hose for feeding melted adhesives from an adhesive-liquifying apparatus to an adhesive-spraying head.
An adhesive conveying hose connects an apparatus for liquifying adhesive masses, such as disclosed in DE-OS No. 28 36 545, with a spraying head for the application of melted adhesive onto the surface of a material. The known hose of the type under consideration includes a central core which is made of a flexible plastic tube which is resistant to the temperatures up to 250.degree. C. This core is surrounded by a steel sleeve and made such that it resists to the inner pressure up to 160 bar. A heating strip or tape is provided in the hose, which is in heat-conducting connection with the central core. The heating tape is helically wrapped around the central core, which is employed to maintain the adhesive in a melted condition.
The heating tape and the central core are covered with a layer of thermal insulation while a protective sleeve of synthetic plastic material or a steel-plate lining is provided on the the outer surface of the layer of thermal insulation. The protective sleeve is provided to prevent heat losses.
The hose can preferably have conduits inside the layer of thermal insulation, these conduits can be provided with temperature feelers or control devices for controlling the operation of the adhesive-spraying head.
In the operation of the apparatus for liquifying masses of adhesive a hot and flowable melted adhesive is supplied under high pressure into the central core of the hose, this adhesive being conveyed by the hose to the adhesive-application head. It is ensured during this operation that the melted adhesive is continually maintained at the range of optimal temperatures by means of the heating tape, temperature feelers and an adjustment device. The inner diameter of the central core is preferably in the range of about 8 mm.
When an adhesive-spraying head is employed as an adhesive-application tool hot melted adhesive should be atomized and applied to the surface of an object in an atomized form.
If cold air is utilized for atomizing a melted adhesive, for example atmosphere air, a non-satisfactory adhesive coat would result on the surface of the object, which would lead to a fast solidifying of the adhesive which is not desired. To avoid this air supplied to the adhesive-spraying head should be preliminarily heated in a special device.
The disadvantage of the known method is not only the fact that the conventional adhesive-application head has been provided with two hoses in place of one, but also that a suitable heating device for heating the supply of pressure air has been required, which heating device must have been also temperature-controlled.